1 Introduction to Transportation Systems

2 PART II: FREIGHT TRANSPORTATION

3 Chapter 14: Railroad Operations

4 Path from Shipper to Receiver Shipper Local Train Train AB Train BC Receiver Train BD Local Train Train EB

5 Blocking Patterns Train AB Train EB Train BC Train BD D and F randomly ordered or D and F traffic is blocked

6 Consolidation  A Key Concept: Consolidation  The railroad system is a high fixed cost system. Take traffic from E and A destined for C and block it into a single set of cars that will go together from B to C at presumably lower cost than in the case of A-C and E-C traffic going separately.

7 Train Operating Costs vs. Train Length Train Operating Costs additional power Train Length (cars) Figure 14.3

8  The operating policy to generate cost savings through consolidation implies stiff penalties when things go wrong. The reason that we run only one train a day from B to C is to achieve long train lengths.  Often we operate with 24-hour service headways; if the cars from E to B destined for this outbound train going to C misses that connection for whatever reason, this can cause a 24-hour delay until the next train.  Think about the impact of these delays on the total logistics costs of the affected receivers. Perhaps a stock-out for our customer results.

9 Cost/Car and Train Length  The cost per car on a long train is clearly going to be much lower than the cost per car on a short train. So there is an incentive to run longer trains from a cost view; that is what drives the idea of low train frequency.  If we run two trains a day between B and C with 50 cars on each rather than 1 train with 100 cars, there is a higher level-of-service associated with a higher train frequency; however, from a cost point of view it is more expensive to run two 50-car trains rather than one 100- car train. Figure 14.4 Cost/Car Train Length (cars)

10 Operations vs. Marketing Perspectives  Now this simple idea relates to “tension” between the operating and the marketing people.Who is going to want to run the 100-car train? The operating person or the marketing person?And who is going to want to run the two 50-car trains? CLASS DISCUSSION

11 Train Dispatching Dispatching Choices Train AB Train BC Train EB Train BC Train CC’ Train CC’’ Train CC’’’ Figure 14.5

12 A Choice in Dispatching Do We “Hold for Traffic”?

13  Delay Propagation on Networks  Network Stability Stable vs. Unstable Equilibrium Stable Equilibrium Unstable Equilibrium Figure 14.6

14 Operating Plan Integrity  Why don’t the railroads just run the trains on schedule as an optimal strategy?  The basic notion is design an operating plan that is feasible and makes sense. You have enough power; you have enough line capacity; you have enough terminal capacity to make this plan actually work.  You run the trains according to plan, that is, according to schedule.

15 “Scheduled” vs. “Flexible” Operation  Is the best strategy “running to plan” in a disciplined manner?  Some railroads feel that is an inflexible, uneconomic way of running the system.  These railroads feel that flexibility for the terminal managers is useful and they can do a better job of balancing service and costs than they can by inflexibly “running to plan”.

16 A Framework for Transportation Operations Operating Plan Philosophy Daily Modified Operating Plan Stochastic Conditions

17 “Daily Modified Operating Plan”  Suppose we have developed, through optimization methods, an “operating plan” which governs the network.  Suppose each day at 6 a.m., railroad management takes that operating plan and from it produces a daily modified operating plan which governs the way the railroad will operate on that particular day.  The operating plan is a base case; the daily modified operating plan is a plan of action for a particular day.  The daily modified operating plan takes account of stochastic conditions on the network like weather and traffic conditions.  It also reflects how much a railroad is willing to change that base operating plan to accommodate conditions on a particular day.

18 How to Define Scheduled vs. Flexible Railroads?  The first way:A scheduled railroad would be one in which the operating plan and the daily modified operating plan were exactly the same.  The second way:A scheduled railroad is one in which there is no difference between the daily modified operating plan decided upon at 6 a.m. and what they actually do that day.